Two-cycle internal combustion engine



P 21, 1965 w. R. CROOKS 3,207,136

TWO-CYCLE INTERNAL COMBUSTION ENGINE Filed March 22, 1965 2 SheetsS heet l I? Y O PRESSURE. -'r

DEGREES OF V ROTAT ION Ex. CLO$E$ mam-nor: IN. OPEN INVENTOR- AUX- o ens WILLIAM R. CRooKs FT 5- maw A'T'T'O RN EYS Sept. 21, 1965 w. R. CROOKS 3,207,136

' TWO-CYCLE INTERNAL COMBUSTION ENGINE Filed March 22, 1965 2 Sheets-Sheet 2 INVENTOR. WILLIAM R. Canons ATTO ENE-Y5 United States Patent 3,207,136 TWO-CYCLE INTERNAL COMBUSTION ENGINE William R. Crooks, Mount Vernon, Ohio, assignor to The Cooper-Bessemer Corporation, Mount Vernon, Ohio, a corporation of Ohio Filed Mar. 22, 1963, Ser. No. 267,180 4 Claims. (Cl. 123-1) The present invention relates to two-cycle internal combustion engines; and more particularly to two-cycle internal combustion engines which use gaseous fuels.

As the piston in a conventional two-cycle engine approaches the bottom of its power stroke, the piston moves past exhaust porting which vents the gases to exhaust, and shortly thereafter it moves past inlet porting, following which air is blown into the cylinder to sweep the cylinder free of exhaust gases and to charge the cylinder with fresh air. Thereafter, the motion of the piston is reversed to move into the cylinder, first closing off the intake ports, then the exhaust ports, and finally compressing the gases for combustion. In most instances the gases are ignited at about before top dead center either by spark ignition or compression ignition. In one type of two-cycle gas engine, for example, the intake ports are closed 40 after bottom center, and the exhaust ports are closed approximately 68 after bottom center. Immediately thereafter a fuel gas is admitted to the cylinder from a separate port usually in the cylinder head, the gases are compressed, and then ignited at approximately 170 after bottom center or 10 before top center. With such an arrangement, the entire mixing time for the gaseous fuel with the air prior to ignition is only approximately 100 of crank shaft rotation.

Because of the relatively short time that is conventionally provided in a two-cycle gas engine for the mixing of the fuel and the air prior to combustion, uneven mixing takes place to produce what is sometimes called stratification of the gases. In certain regions of the cylinder, the mixture will be richer than the desired proportion of natural gas to air, and in other regions of the cylinder they will be leaner than the desired mixture. It is desired that the mixture that is supplied to a twocycle engine be a predetermined one which is less than stoichiometric proportions of the fuel to the air, so that a desired rate of burning will ensue. Mixtures that are leaner than the desired ratio burn too slowly, while mixtures that are richer than the desired ratio burn too quickly. Where stoichiometric proportions of fuel to air are provided, spontaneous ignition or detonation may take place if the compression ratio is greater than approximately 8:1. Because uneven mixing or stratification takes place in most two-cycle gas engines, it is necessary that the ignition be retarded to take place at a time which will not produce detonation for the richest mixture that occurs in the cylinder; and it is also necessary that the compression ratio of the engine be less than that at which detonation for stoichiometric mixtures occurs.

By way of contrast, a four-cycle engine provides approximately 300 of crank shaft rotation for the mixing of the fuel and air, a period that is nearly three times as long as the available mixing period in a conventional two-cycle engine. By reason of the better mixing which is provided in the four-cycle engine, its compression ratio can be as high as 10:1 or 12:1, and its ignition can be timed to take place at approximately 20 before top center without detonation. Because of these conditions higher pressures can be utilized in four-cycle gas engines over greater degrees of crank shaft rotation than can be utilized in a two-cycle gas engine; so that the efiiciency of the four-cycle engine is greater than that of the two- 3,207,136 Patented Sept. 21, 1965 cycle engine by approximately 10%. This means that in general the four-cycle engine has a fuel consumption which is less than that of a two-cycle engine of comparable horsepower by approximately 10%.

The principal object of the present invention is the provision of a. new and improved method and apparatus for improving the degree of mixing of the fuel and the air in a two-cycle internal combustion engine prior to combustion.

A more detailed object of the present invention is the provision of a new and improved two-cycle internal combustion engine having an auxiliary charge preparation chamber that is in valved communication with the top portion of its combustion chamber, said engine including valve means which will allow the engine to compress gases into the auxiliary chamber during the initial portion of its compression stroke, and thereafter isolate the auxiliary chamber from the combustion chamber, together with means to fill the auxiliary charge preparation chamber with gaseous fuels which are mixed during the interval representing the balance of the compression and succeeding power stroke While combustion, exhaust and scavenging are proceeding in the main cylinder. On the next inward stroke of the piston the auxiliary chamber opened to communicate with the combustion chamber to cause a pre-mixed charge to enter the cylinder promptly after its exhaust gases have been purged and the cylinder scavenged.

The invention resides in certain constructions, and combinations, and arrangements of parts, and further objects and advantages of the present invention will become apparent from the following description of a preferred embodiment, described with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic vertical view, with parts in section, of a two-cycle gas engine embodying the present invention;

FIG. 2 is a sectional view of the auxiliary mixing and charge preparation chamber shown in FIG. 1; and

FIG. 3 is a schematic indicator card which shows the general changes in the pressure of the cylinder at various degrees of rotation of the crank shaft.

Referring to FIG. 1 there is shown diagrammatically one cylinder of a two-cycle gas engine. The cylinder block is designated generally 10, and has a cylinder 11 therein in which a piston 12 is fitted for reciprocatory movement. The piston 12 is suitably pinned to a connecting rod 13 which in turn is rotatably fixed to a crank shaft 14. The upper end of the cylinder chamber 11 is closed off by a cylinder head 15. In the engine shown ignition is caused by a spark plug 16 seated in the cylinder head, although it should be understood that other igniting systems may be used.

The cylinder head 15 also includes a housing designated generally 17 which forms an auxiliary charge preparation chamber whose purpose will later be explained. Suitable exhaust ports 18 are provided in one side of the engine cylinder 11, so that as the piston 12 approaches the bottom of its power stroke, the burned gases are exhausted through the exhaust port. The opposite side of the cylinder chamber 11 is provided with intake ports 19 which allow air under pressure to enter into the cylinder chamber 11 to scavenge the cylinder chamber at the very bottom of the power and compression strokes as is Well understood in the art.

The auxiliary chamber housing 17 encloses an auxiliary charge preparation chamber 20 that has a volume of approximately one-third of the displacement of the cylinder chamber 11.

The charge preparation chamber 20 is placed into communication with the engine cylinder almost immediately ICC after the cylinder has been scavenged and charged with fresh air. As will be subsequently described, the charge preparation chamber contains a fuel rich mixture which will form an ultimately combustible mixture in the engine cylinder. Communication between the engine cylinder and the charge preparation chamber continues for a sufficient period of time to insure that a complete intermingling of the gases in the two chambers takes place. Thereafter, the charge preparation chamber 20 is cut off from communication with the engine cylinder, and a fuel valve is opened to admit gas under pressure to the charge preparation chamber. The .gas has ample time to mingle with the gas already in the chamber while compression, ignition and combustion take place in the separated engine cylinder. Reference will be made to an indicator diagram showing a preferred sequence of operations. In order to control the operation of the auxiliary charge preparation chamber 20, there must be provided a valve structure 22 for controlling communication between the auxiliary chamber 20 and the engine cylinder 11, and another valve structure 23 for controlling communication of the fuel supply line 21 with the auxiliary chamber 20. In the embodiment shown in the drawing, the valves 22 and 23 are connected together and positioned in a single flanged valve barrel 24 so that the valves 22 and 23 can be assembled externally of the housing 17 and installed as a unit.

In the embodiment shown in the drawing, the auxiliary chamber housing 17 is bored from one side to provide a vertical extending opening 25 through its external wall as well as an aligned stepped opening 26 through the wall which separates the auxiliary chamber 20 from the engine cylinder 11. The flanged valve barrel 24 is positioned in the aligned openings 25 and 26 with its lower end positioned against the stepped portion 27 of the opening 26, and its flange 28 bolted down upon a gasket 29 seated on the exterior surface of the housing 17.

The inner valve structure 22 is formed by an annular valve seat 30 positioned on the inner end of the valve barrel 24 surrounding a valve port 31 which communicates the auxiliary chamber 20 and the engine cylinder 11. The valve port 31 is adapted to be closed off by the head 32 of a poppet valve 33. The stem 34 of the poppet valve 33 extends upwardly through the valve barrel 24 to a point externally of the housing from which it can be operated.

The outer valve structure 23 is formed by a cylindrical sliding sealing plug member 35 which fits into the central opening 36 of a cooperating valve sleeve 37 positioned in the upper end of the valve barrel 24. The valve sleeve 37 has a plurality of radially extending valve ports 38 therethrough which align with a groove 39 in the valve barrel 24. Gas is always communicated to the groove 39 from the supply line 21 through passageways 40 and 41 in the housing 17 and valve barrel 24, respectively. The outer end of the plug member 35 forms a land portion 42 which forms a sliding seal with the sleeve 37, and which is adapted to close 011 the valve ports 38 when the plug member moves in over the valve ports 38. The sliding sealing land portion 42 terminates at its inner end in a recess 43 inwardly of which the plug is of reduced diameter and suitably grooved longitudinally to always communicate the recess 43 of the plug member 35 with the auxiliary chamber 20. The plug member 35 is positioned longitudinally of the stem 34 so that the recess 43 of the plug member 35 opens communication between the valve ports 38 and the auxiliary chamber 20 when the head 32 of the inner poppet valve 33 is on its seat 30. The poppet valve 33 is provided with a shroud 44 which closely fits into the inner valve port 31 between the auxiliary chamber 20 and the valve seat 30. The shroud 44 is of such axial length as to keep the valve port 31 closed during the initial downward movement of the valve stem 34 until the land portion 42 of the valve plug member 35 has closed 011 the valve ports 38 which communicate fuel to the auxiliary chamber 20. The valves thus operate so that there is never a direct communication between the fuel line 21 and the engine cylinder 11. A washer 45 is positioned against the bottom of the valve plug member 35 to cause the gas entering the auxiliary chamber to be directed radially to produce a swirling motion. The valve stem 34 is biased upwardly by a coil spring 46 that is positioned between the washer 45 and the bottom of the valve barrel 34 to normally close valve 23 and open valve 22. The valve sleeve 37 is provided with a flange 47 that is seated against a shoulder 48 in the upper end of the valve barrel 24. Packing 49 is positioned around the valve plug member 35 on top of the sleeve 37 and the assembly is held in place by the cover plate 50. The top end of the valve stem 34 is provided with a cam follower 51 that rides against a cam 52 which is driven in timed relation with the engine crank shaft 14.

The operation of the engine so far described can best be understood by the indicator card diagram shown in FIG. 3 of the drawings. When the piston 12 is in its bottom center position both the exhaust port 18 and the inlet portion 19 are open so that scavenging air (usually under pressure) forces the burned gases in the cylinder chamber 11 out through the exhaust port 18. At approximately 44 after bottom center, the piston 12 closes the intake ports 19, and at approximately 66 after bottom center the piston closes the exhaust ports 18. At approximately 68 after bottom center the cam 52 presses down upon the valve stem 34 to cause the cylindrical outer land portion 42 of the valve structure 22 to seal off the radial gas valve ports 38 of the gas inlet valve 22, and at approximately 70 after bottom center, the shroud 44 is lifted clear of the valve seat 30 to communicate the auxiliary chamber 20 to the engine cylinder 11.

The mixture of air and fuel gas that is contained within the auxiliary chamber 20 and which may be at about 200 pounds per square inch pressure is communicated to the side of the cylinder chamber 11 toproduce a swirlting, mixing action with the fresh air supply that is contained in the engine cylinder at this time. Upward movement of the piston 12 thereafter compresses the gas mixture that is within the cylinder, causing part of it to flow up into the auxiliary chamber 20, and this continues to about after bottom center when the shroud 44 moves up into the valve port 31. At this time the pressure in the auxiliary chamber is approximately 15 0 pounds per square inch. At approximately after bottom center, the head 32 is in complete engagement with the valve seat 30, and the annular recess 43 is full open with respect to the radial valve ports 38 of the gas valve 22 to allow gas from the fuel supply line 21 to flow past a throttle valve 54 to the auxiliary chamber 20.

While the gas is mixing in the auxiliary charge preparation chamber 20, the gases in the engine cylinder 11 continue to be compressed until .after bottom center when ignition is caused by the spark plug 16. At this time the pressure in the cylinder may be 250 pounds per square inch, and after ignition, the pressure will continue to increase to a nominal peak firing pressure of around 750 pounds per square inch during which the piston 12 is moving downwardly. At approximately 66 before bottom center, the exhaust port 18 is opened by the piston 12 to exhaust the burned gases from the cylinder chamber 11, and at 44 before bottom center, the piston 12 moves past the intake port 19 to allow a new charge of air under pressure to enter the cylinder chamber 11 and thereby scavenge the same.

All during the power stroke, while the piston 12 is moving downwardly, gas from the supply line 21 may be admitted to and mixed in the auxiliary charge preparation chamber 20 so that the pressure in the auxiliary chamber can, under overload conditions, assume nearly the same pressure as is provided in the gas header 21. This pressure may be as high as 200 pounds per square inch.

It will now be seen that the gaseous fuel is allowed to mix with the air that has been initially trapped Within the auxiliary chamber 20 from a point 135 after bottom center, through the entire power stroke, and then through 170 of the next compression stroke before they are ignited. This permits mixing during approximately 395 of crank shaft rotation. For approximately 295 of the 395, gas is being mixed with the air in the auxiliary chamber 20, which constitutes approximately one-third of the total volume of the combination chamber 11, following which the contents of the auxiliary charge preparation chamber 20 are discharged with a swirling motion into the engine cylinder 11. For the remaining 100 of crank shaft rotation the gases from the auxiliary chamber 20 are mixed with the air in the engine cylinder 11 with a considerable amount of turbulence so that a substantially complete mixture is obtained.

It will be seen that the objects heretofore enumerated as well as others have been accomplished, and that there has been provided a method and means for producing substantially complete mixing of gaseous fuels and intake air in a two-cycle internal combustion engine.

While the invention has been described in considerable detail, I do not wish to be limited to the particular embodiment shown and described, and it is my intention to cover hereby all novel adaptations, modifications, and arrangements thereof which come within the practice of those skilled in the art to which the invention relates.

What I claim is:

1. A method of increasing the degree of mixing of fuel and air in an internal combustion engine having an engine cylinder and a piston which reciprocates between a top posit-ion in said cylinder and a bottom position in said cylinder to provide a power stroke when the piston moves towards the bottom of the chamber and a compression stroke when the piston moves toward the top of the chamber, said method comprising, compressing unburned gases from said engine cylinder into an auxiliary charge preparation chamber during a part of a compression stroke, then isolating the charge preparation chamber from the engine cylinder during the remainder of the compression stroke and the power stroke, introducing a fuel into said charge preparation chamber after it is isolated from the engine cylinder to mix with the gases already in said chamber, while combustion, expansion and scavenging is taking place and communicating the cylinder after the scavenging has taken place to charge the engine cylinder with a fuel-air mixture.

2. The method defined in claim 1 in which the fuel introduced into said charge preparation chamber is a gaesous fuel.

3. In an internal combustion engine, having a cylinder, a crankshaft, a piston in said cylinder operatively connected to said crankshaft, an enclosed charge preparation chamber communicating with said cylinder, first valve means for isolating said chamber from said cylinder, said engine having a power stroke as said piston moves down said cylinder and a compression stroke as said piston moves up in said cylinder, air inlet means including valve porting for forcing air into said cylinder at the bottom of the compression stroke, means sequentially opening said first valve means at the beginning of a compression stroke after said valve porting of said air inlet means is closed, and closing said first valve means after said piston has proceeded a predetermined distance on said compression stroke and at a time when pressure in said charge preparation chamber has equalized with that of said cylinder and inlet air from said cylinder has been forced back into said charge preparation chamber, and second valve means positively actuated for introducing gaseous fuel under pressure into said chamber while said first valve means is closed, whereby said fuel charge is mixed in said chamber with air from said cylinder until said first valve means is next opened.

4. An internal combustion engine in accordance with claim 3 operating on a two-stroke cycle and wherein said charge preparation chamber has a volume equal to approximately /3 of the displacement of said piston,

References Cited by the Examiner UNITED STATES PATENTS 1,467,998 9/23 Brown 123-75 1,679,286 7/28 Zaikowsky 123-1 FOREIGN PATENTS 587,531 1/25 France.

OTHER REFERENCES German Printed Application (Janicke), 1,098,287, 1/ 26/ 61.

FRED E. ENGELTHALER, Primary Examiner, 

1. A METHOD OF INCREASING THE DEGREE OF MIXING OF FUEL AND AIR IN AN INTERNAL COMBUSTION ENGINE HAVING AN ENGINE CYLINDER AND A PISTON WHICH RECIPROCATES BETWEEN A TOP POSITION IN SAID CYLINDER AND A BOTTOM POSITION IN SAID CYLINDER TO PROVIDE A POWER STROKE WHEN THE PISTON MOVES TOWARDS THE BOTTOM OF THE CHAMBER AND A COMPRESSION STROKE WHEN THE PISTON MOVES TOWARD THE TOP OF THE CHAMBER, SAID METHOD COMPRISING, COMPRESSING UNBURNED GASES FROM SAID ENGINE CYLINDER INTO AN AUXILIARY CHARGE PREPARATIN CHAMBER DURING A PART OF A COMPRESSION STROKE, THEN ISOLATING THE CHARGE PREPARATION CHAMBER FROM THE ENGINE CYLINDER DURING THE REMAINDER OF THE COMPRESSION STROKE AND THE POWER STROKE, INTRODUCING A FUEL INTO SAID CHARGE PREPARATION CHAMBER AFTER IT IS 